Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
  • C08L23/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
  • C08L23/22—Copolymers of isobutene; Butyl rubber ; Homo- or copolymers of other iso-olefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes

Definitions

• ABS CT A mouldable blend of a thermoplastic elastomeric Jan. 28, 1969 Canada ..041,284 block copolymery an elastomeric isobutylene polymer and optionally, a resinous polymer of monoalkenyl 52 us. Cl.
• aromatic hydrocarbon is used in the manufacture of Int C C08 29/12 C08f moulded soft rubber goods, e.g., pharmaceutical eno s 6 6 I s I l l [58] Field of Search ..260/876 B C owes 10 Claims, No Drawings IMPERMEABLE POLYMERIC COMPOSITIONS
• This invention relates to polymeric compositions. More particularly, it relates to elastomeric thermoplastic polymer compositions of improved air impermeability.
• Polymers exhibiting the properties of both a thermoplastic and an elastomer are known. These polymers comprise block copolymers having two terminal polymeric blocks of a thermoplastic polymer, for example polystyrene or polyalphamethylstyrene, and at least one non-terminal block of an elastomeric polymer, for example polybutadiene or polyisoprene.
• Typical examples of such block copolymers are those of general form polystyrene-polybutadiene-polystyrene and polyalpharnethyl-styrene-polybutadienepolyalphamethylstyrene.
• block copolymers exhibit the properties of elastomers, i.e., elongation at break of greater than 100 percent and rapid retraction to approximately their original length after removal of the elongating stress, without curing. They are also thermoplastic, so that they can be molded by conventional molding techniques. They resume their elastomeric properties on cooling and solidifying.
• thermoplastic elastomers can be enhanced by blending therewith an isobutylene polymer, for example butyl rubber (a copolymer of isobutylene with small amounts of isoprene).
• isobutylene polymer for example butyl rubber (a copolymer of isobutylene with small amounts of isoprene).
• the present invention provides a polymeric composition
• a polymeric composition comprising 100 parts by weight of a thermoplastic elastomeric block copolymer and from about 5 to about 250 parts by weight of an isobutylene polymer.
• the preferred block copolymers for use in the present invention are those in which the thermoplastic terminal blocks are of polyalpharnethylstyrene or polystyrene, and the elastomeric non-terminal block is a polymer of a conjugated diolefinic hydrocarbon.
• Block copolymers of general form polyalpharnethylstyrene-polybutadiene-polyalphamethylstyrene are especially preferred, on account of their superior high temperature physical properties.
• the most suitable isobutylene polymers include solid polyisobutylene and butyl rubber, with butyl rubber being the most preferred polymer.
• Butyl rubber is a high molecular weight copolymer of isobutylene with less than percent, preferably less than 5 percent of one or more C C diolefins such as isoprene, divinylbenzene, pentadiene-l,4.
• the isobutylene polymers which are used in this invention are solid plasticdeformable materials which do not exhibit the properties of an elastomer unless vulcanized.
• Methods of preparation of the suitable block copolymers are well known per se, and do not comprise a part of the present invention. Briefly, they involve polymerization of the first, thermoplastic forming monomer by means of an anionic polymerization, initiator such as butyl lithium and after complete polymerization, addition of a charge of monomer to form the elastomeric block to the non-deactivated polymerization reaction mixture. After complete polymerization of the second monomer, a further monomeric charge is added to the non-deactivated polymer, to form a three-block copolymer. Such polymerimtion of alphamethylstyrene is best carried out at low temperatures and in the presence of small amounts of a polar solvent.
• the preparation of the isobutylene polymer is well known per se, and does not comprise part of the present invention. Such preparation involves cationic polymerization of the monomers at low temperatures.
• the method of blending the block copolymer and the isobutylene polymer is preferably by mill mixing at elevated temperatures or by mixing in internal mixers.
• the method is not critical, provided that an intimate dispersion of the two polymers is achieved.
• Other methods, such as solution blending, may also be employed.
• the blends of the present invention show greatly enhanced air impermeability, as previously mentioned, along with increased softness and decreased modulus of extension.
• the other physical properties of the block copolymers are largely retained. While these properties make the blends ideally suitable for some applications, such as pharmaceutical enclosures, as discussed below, it is in some cases desirable to have thermoplastic elastomeric compositions with good air impermeability, along with increased tear strength and a hardness similar to that of the raw block copolymer.
• minor amounts of a polymer of a monoalkenyl substituted aromatic hydrocarbon, such as polystyrene may be added to the block copolymer-isobutylene polymer blends.
• a polymeric composition comprising parts by weight of a thermoplastic elastomeric block copolymer, from about 5 to about 250 parts by weight of an isobutylene polymer, and up to about 50 parts by weight of a polymer of a monoalkenyl substituted aromatic hydrocarbon.
• a block copolymer of general form polyalphamethylstyrene-polybutadienepolyalpharnethylstyrene from about 10 to about 60 parts by weight of butyl rubber and from about 10 to about 20 parts by weight of polystyrene.
• These threecomponent blends additionally have improved tear strength and are well suited for preparation of molded or calendered shoe soles.
• The'two-component blends of the present invention are particularly suitable for the manufacture of caps, stoppers and the like enclosures for sealing containers for pharmaceutical preparations. They have a high degree of imperrneability to air, thus protecting the pharmaceutical preparations in the container from the possible harmful effects of contact with air.
• compositions of the present invention are self-sealing, i.e., they can be pierced with a syringe needle having a diameter of about one-fifteenth of an inch or less and after withdrawal of the needle, the composition closes up and seals again.
• the self-sealing property is associated with the correct degree of softness and elasticity of the polymeric compositions, so that passage of the syringe needle therethrough does not lead to removal or permanent displacement of any of the composition contacted by the needle during its passage.
• these compositions are thermoplastic and moldable so that enclosures of the desired shape can be readily formed from them by well-known molding techniques, in con trast with conventional rubbers. After molding, they will withstand sterilization temperatures of up to about 1 C and procedures to which pharmaceutical enclosures must be subjected.
• compositions acquire the above desirable properties for this use withoutthe necessity of compounding or curing them, so that the risk of having residual biologically active ingredients in the polymeric compositions, left over from the curing process, a danger which is always present with conventional rubbers, is avoided.
• the compositions may contain small amounts of suitable inert pigments for decorative purposes, or for purposes of identifying various grades of compositions.
• EXAMPLE 1 A block copolymer of general polyalphamethyl-styrene-polybutadienepolyalphamethylstyrene (hereinafter referred to as 0.8a block copolymer) was prepared, blended with different quantities of uncured butyl rubber, and the physical properties of the resultant polymeric blends tested.
• 0.8a block copolymer general polyalphamethyl-styrene-polybutadienepolyalphamethylstyrene
• the aBa block copolymer had an alphamethylstyrene content of approximately 35 weight percent and a molecular weight of about 60,000. It was prepared by the stepwise addition, anionic polymerization method outlined previously.
• the air permeability was measured by measuring the volume of air (corrected to N.T.P.) which will pass through a sealing plug of the composition of area 1 square cm. and thickness 1 cm., under a differential pressure of 1 atmosphere, in unit time.
• the self-scalability of the composition was estimated by means of the following empirical test.
• a molding of the composition of about 4mm thickness was pierced with a gauge 15 syringe needle, the needle withdrawn, and after a lapse of about 15 seconds the molding was subjected to a hydrostatic pressure of about 0.25 p.s.i. This was done by supporting a 7-inch column of water on the pierced plug. If the leakage of the water occurred through the plug, its self-sealability was ranked as poor. If no leakage occurred over a considerable period of time, its self-scalability was ranked as good.
• moldings from the blended compositions were immersed in boiling water to simulate sterilization conditions to which pharmaceutical enclosures are subjected. No distortion was observed with any of these moldings.
• EXAMPLE 2 In this example, three further blends of aBa block copolymer of Example 1 and butyl rubber were prepared as in Example 1, using different proportions of ingredients, and the air permeability of samples molded from the blend measured in the same way. These results are given in Table 2.
• thermoplastic elastomeric composition of improved air impermeability comprising parts by weight of a thermoplastic elastomeric block copolymer, wherein the thermoplastic terminal blocks are selected from polystyrene and polyalphamethylstyrene and the non-terminal elastomeric block is a polymer of a conjugated diolefinic hydrocarbon, and from about 5 to about 250 parts by weight of an isobutylene polymer selected from polyisobutylene and butyl rubber, said composition being free of curing agent.
• thermoplastic copolymer is polyalphamethylstyrene- Bassist" aglls ress zsss. e, strait a alphamethylstyrene.
• composition of claim 2 wherein the elastomeric polymer block is polybutadiene.
• composition of claim 2 wherein the isobutylene polymer is butyl rubber.
• composition of claim 1 which additionally comprises up to 50 parts by weight of a polymer of a monoalkenyl substituted aromatic hydrocarbon.
• composition of claim 5 wherein the additional polymer is polystyrene.
• composition of claim 6 comprising 100 parts by weight of a block copolymer of general form polyalphamethylstyrene-polybutadienepolyalphamethylstyrene, from about 10 to about 60 parts by weight of butyl rubber, and from about 10 to about 50 parts by weight of polystyrene.
• a polymeric composition of claim 2 wherein the isobutylene polymer is butyl rubber used in an amount of from about 30 to about 50 parts by weight per 100 parts of block.
• composition of claim 2 which comprises a major proportion of butyl rubber, and in which the block copolymer has a tensile strength of at least 200 Kg.cm

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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Cited By (17)

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Citations (5)

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• 1969
  • 1969-01-28 CA CA857965A patent/CA857965A/en not_active Expired
  • 1969-12-09 GB GB1250088D patent/GB1250088A/en not_active Expired
  • 1969-12-11 US US884365A patent/US3686364A/en not_active Expired - Lifetime
• 1970
  • 1970-01-19 NL NL7000723.A patent/NL160862C/xx not_active IP Right Cessation
  • 1970-01-21 DE DE2002579A patent/DE2002579C2/de not_active Expired
  • 1970-01-27 FR FR7002794A patent/FR2029555A1/fr not_active Withdrawn
  • 1970-01-27 CH CH111070A patent/CH519534A/fr not_active IP Right Cessation
  • 1970-01-27 BE BE744975D patent/BE744975A/xx unknown

Patent Citations (5)

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